Registering a 3D image data of the chest with fluoroscopic images may be carried out by directly comparing virtual fluoroscopic images with real fluoroscopic images. Various anatomical features are used to register the images including but not limited to the heart and diaphragm. The heart and diaphragm, however, have significant size compared to other features and thus can incorrectly bias the registration results towards aligning the heart and diaphragm.
An example of an inaccurate registration 10 suffering from the shortcoming described above is shown in FIG. 1. Projected virtual rib 12 is shown off-set from fluoroscopic rib 14. The off-set arises due to an overemphasis on aligning the diaphragm 16. This bias/error increases due to the difference in breathing level (and heart beat activity) between 3D image and fluoroscopic image.
Accordingly, techniques for registration are desired that avoid the above described shortcomings.